Like a copying machine, a system which generates digital image data by scanning a document and printing it after image processing is applied to the digital image data is available. In such system, a method of obtaining a copy output with high image quality by determining image attributes for respective pixels or blocks of input image data, and applying optimal image processing to each attribute is known.
For example, Japanese Patent No. 3,023,374 discloses a method of analyzing image data obtained by scanning a document to separate the image data into at least two regions, i.e., a character region and grayscale image region, and selectively applying first and second image processes to these regions. The first and second image processes include color conversion processing such as color correction, undercolor removal, and the like, and edit processing such as mosaic image conversion, mirror image conversion, and the like in addition to processing for selectively smoothing or sharpening the character region and grayscale image region to desired levels. Also, means for manually setting parameters used in these image processes is equipped.
On the other hand, when a digital document generated by a computer or the like is to be printed out, data (PDL data) described in a page description language is interpreted. Then, attribute information of each object is obtained, and image processing for printing is selectively used for character data or photo data in accordance with the attribute information to obtain a printout with high image quality. Such method is also known.
For example, Japanese Patent Laid-Open No. 6-320802 discloses a method of outputting an image by interpreting PDL data generated by a host computer, generating object information indicating each image element, and executing processing based on the generated information upon reception of the PDL data.
These techniques are carried out to improve the image quality of an output in consideration of the fact that preferred image qualities tend to differ for respective objects which form an image. That is, there is a tendency to place an importance on sharpness and contrast for a character region, and to place an importance on smooth tone reproduction for a photo region. Furthermore, in some cases, the parameters of these processes are preferably set in consideration of characteristics for respective models of printers and for each individual printer so as to attain optimal image reproduction in correspondence with the characteristics of printers and color materials.
As means for printing out digital data received from outside the apparatus, apparatuses which not only have a facsimile print function and PDL data print function but also have print functions of e-mail and Internet facsimile (IFAX) and the like are commercially available in recent years.
Attribute information or information used to generate attribute information is often not appended to received data to be printed. In this case, the image processing methods and image processing parameters executed in the apparatus are set without exception independently of the received data, or after attribute determination processing is executed for the received data, the image processing methods and image processing parameters suited to attributes are set. If the same image processing methods and image processing parameters are set, an output that the user does not want may be output each time by executing processing which does not match the purpose of output or user's favor in terms of image quality. On the other hand, if the attribute determination processing is executed for the received data, not only high processing cost is required, but also a long processing time is required depending on the characteristics of the received data, resulting in a considerable drop of the apparatus performance.